1. Field of the Invention
The present invention relates to a fixing belt used in image forming apparatuses such as electrophotographic copiers and printers for fixing a toner image, formed on a recording medium, to the recording medium; a fixing unit employing the fixing belt; and an image forming apparatus employing the fixing unit. More particularly, the invention relates to an arrangement wherein the fixing belt with a lubricant applied to its inside surface is driven into rotation and is pressed against the recording medium formed with the toner image thereon so as to fix the toner image to the recoding medium, and is characterized by preventing the lubricant applied to the inside surface of the fixing belt from leaking out of the belt.
2. Description of the Related Art
In the image forming apparatuses such as electrophotographic copiers and printers, it has been a conventional practice to fix the toner image, formed on the recording medium, to the recording medium by means of the fixing unit.
Conventionally, various types of fixing units have been used for fixing the toner image, formed on the recording medium, to the recording medium.
One of such fixing units has the following arrangement as shown in FIG. 1. An endless fixing belt 21 is pressed against a rotating pressure roller 23 by means of a pressing member 22 disposed at place inside of an inside surface of the fixing belt. In conjunction with the rotation of the pressure roller 23, the fixing belt 21 is driven into rotation by way of a force of friction between the pressure roller 23 and the fixing belt 21. On the other hand, a heat roller 24 containing therein a heating element 24a is disposed at place inside of the inside surface of the fixing belt, so that the fixing belt 21 is heated by the heat roller 24.
In the fixing unit, a sheet-like recording medium 9 formed with a toner image t thereon is oriented in a manner to present the toner image t to the fixing belt 21 and is guided into space between the fixing belt 21 and the pressure roller 23. The recording medium 9 is heated and pressurized as sandwiched between the fixing belt 21 and the pressure roller 23, whereby the toner image t is fixed to the recording medium 9.
It is an object of the invention to solve the aforementioned problem encountered when the toner image formed on the recording medium is fixed to the recording medium by means of the fixing unit employing the fixing belt. Specifically, in the case where the lubricant such as a grease is applied to the inside surface of the fixing belt, the invention is directed to prevent the leakage of the lubricant from the fixing belt so as to ensure the consistent image fixation over an extended period of time.
A fixing belt according to the invention is used in a fixing unit which drivingly rotates an endless fixing belt having the lubricant applied to the inside surface thereof and which presses the fixing belt against a recording medium formed with a toner image thereon thereby fixing the toner image to the recording medium, wherein the inside surface of the fixing belt is formed with a plurality of grooves extended along a circumferential direction of the fixing belt or extended from a widthwise center of the fixing belt toward the opposite ends thereof as inclined in a moving direction of the fixing belt.
A fixing unit according to the invention comprises: an endless fixing belt having a lubricant applied to an inside surface thereof; a driver for drivingly rotating the fixing belt; and a pressing member for pressing the fixing belt on the inside surface thereof thereby pressing the fixing belt against a recording member, wherein the inside surface of the fixing belt is formed with a plurality of grooves extended along a circumferential direction of the fixing belt or extended from a widthwise center of the fixing belt toward the opposite ends thereof as inclined in a moving direction of the fixing belt.
An image forming apparatus according to the invention comprises: an image carrier; an electrostatic latent image forming unit for forming an electrostatic latent image on the image carrier; a developing device for forming a toner image on the image carrier by developing the electrostatic latent image; a transfer unit for transferring the toner image from the image carrier to a recording member; and a fixing unit for fixing the transferred toner image to the recording member, wherein the fixing unit comprises: an endless fixing belt having a lubricant applied to an inside surface thereof; a driver for drivingly rotating the fixing belt; and a pressing member for pressing the fixing belt on the inside surface thereof thereby pressing the fixing belt against the recording member, the inside surface of the fixing belt formed with a plurality of grooves extended in a circumferential direction of the fixing belt or extended from a widthwise center of the fixing belt toward the opposite ends thereof as inclined in a moving direction of the fixing belt.
The following advantage may be obtained by forming the plural grooves in the inside surface of the fixing belt where the lubricant is applied, the grooves extended along the circumferential direction of the fixing belt, as described above. When the toner image is fixed to the recording medium by pressing the fixing belt, being drivingly rotated, against the recording medium formed with the toner image thereon, the lubricant applied to the inside surface of the fixing belt is retained in the aforesaid plural grooves extended along the circumferential direction. As a result, the lubricant is properly prevented from leaking from the widthwise opposite ends of the fixing belt.
Furthermore, the following advantage may be obtained by forming the plural grooves in the inside surface of the fixing belt where the lubricant is applied, the grooves extended from the widthwise center of the fixing belt toward the opposite ends thereof as inclined in the moving direction of the fixing belt. When the toner image is fixed to the recording medium by pressing the fixing belt, being drivingly rotated, against the recording medium formed with the toner image thereon, the lubricant applied to the inside surface of the fixing belt is guided to the widthwise center of the fixing belt via the grooves extended from the widthwise center toward the opposite ends as inclined in the moving direction of the fixing belt. As a result, the lubricant is more assuredly prevented from leaking from the widthwise opposite ends of the fixing belt.
As suggested by the fixing unit according to the invention, the following advantage may be obtained by using the aforementioned fixing belt in a case where the endless fixing belt with the lubricant applied to the inside surface thereof is drivingly rotated and is pressed against the recording medium formed with the toner image thereon for fixing the toner image to the recording medium. That is, the lubricant applied to the inside surface of the fixing belt is prevented from leaking from the widthwise opposite ends of the fixing belt, as described above. Thus is obviated the problem encountered by the conventional fixing units, that the lubricant leaks from the widthwise opposite ends of the fixing belt, disabling the proper drivable rotation of the fixing belt. As a result, the toner image to be fixed to the recording medium is prevented from suffering disturbances or the recording medium is prevented from being jammed. Hence, the consistent image fixation may be ensured over an extended period of time, so that favorable image formation may be provided over an extended period of time.
As suggested by the image forming apparatus according to the invention, the following advantages may be obtained by employing the aforementioned fixing unit for fixing the toner image to the recording medium. The toner image to be fixed to the recording medium is prevented from suffering disturbances or the recording medium is prevented from being jammed. Hence, the consistent image fixation may be ensured over an extended period of time, so that favorable image formation may be provided over an extended period of time.
These and other objects, advantages and features of the invention will become apparent from the following description taken in conjunction with the accompanying drawings which illustrate specific embodiments of the invention.